Basic Concepts in Wireless LAN
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Transcript of Basic Concepts in Wireless LAN
Basic Concepts in Wireless LAN
Shashikant V. AthawaleAssistant Professor
Department of Computer Engineering, AISSMS COE ,Pune
Wireless Standard
Wireless LAN And Technology
Wireless Application Protocol
Content
There have been 5 major milestones in wireless internet communication.◦ 802.11 – Released in 1997, the original wireless protocol◦ 802.11a – Released in late 1999◦ 802.11b – Released in late 1999◦ 802.11g – Released in mid 2003◦ 802.11n – Released in 2009
Wireless Standard
The ORIGINAL wireless protocol.◦ Security implemented via WEP
Wired Equivalent Privacy (Legacy) Provided Bandwidth
◦ 1 or 2 Mbit/s due to use of CSMA/CA Relatively Unpopular Low interoperability due to loose specifications Used DSSS Considered Legacy and no longer used
802.11 – 1997
One of two amendments to the original 802.11
specification released simultaneously
Provided up to 54 Mbit/s bandwidth
Uses OFDM
◦ Orthogonal Frequency-Division Multiplexing
Transmits a signal over several sub signals for higher efficiency
802.11a
Second of two amendments released in 1999
Provided up to 11 Mbit/s bandwidth
Uses DSSS
◦ Direct-Sequence Spread Spectrum
Transmits a signal over several sub signals for higher efficiency
802.11b
Pretty much the most common wireless network in use
today.
Operates on 2.4Ghz band
Provides up 54Mbit/s bandwidth
◦ 108Mbit/s with special implementations
Uses OFDM for modulation
Adopted quickly after release for cheap and high bandwidth
802.11g
Newest member of the 802.11 family.
Has rated 600Mbit/s bandwidth
Introduces MIMO
◦ Multiple-Input Multiple-Output
OFDM Modulation
◦ Uses higher frequencies for increased number of carrier waves
802.11n
A wireless LAN uses wireless transmission medium
Used to have high prices, low data rates, occupational
safety concerns, and licensing requirements
Problems have been addressed
Popularity of wireless LANs has grown rapidly.
Wireless LAN And Technology
Saves installation of LAN cabling Eases relocation and other modifications to network structure However, increasing reliance on twisted pair cabling for LANs
◦ Most older buildings already wired with Cat 3 cable◦ Newer buildings are prewired with Cat 5
Wireless LAN to replace wired LANs has not happened In some environments, role for the wireless LAN
◦ Buildings with large open areas Manufacturing plants, stock exchange trading floors, warehouses Historical buildings Small offices where wired LANs not economical
May also have wired LAN◦ Servers and stationary workstations
Application-LAN Extension
Single Cell Wireless LAN Configuration
Multi-Cell Wireless LAN Configuration
Infrastructure Wireless LAN
Peer-to-peer network
Set up temporarily to meet some immediate need
E.g. group of employees, each with laptop or palmtop,
in business or classroom meeting
Network for duration of meeting
Ad Hoc Networking
Ad Hoc LAN
Same as any LAN: High capacity, short distances, full connectivity, broadcast capability.
Throughput: efficient use wireless medium Number of nodes:Hundreds of nodes across multiple cells Connection to backbone LAN: Use control modules to connect to both types of
LANs Service area: 100 to 300 m Low power consumption:Need long battery life on mobile stations Transmission robustness and security:Interference prone and easily
eavesdropped Collocated network operation:Two or more wireless LANs in same area License-free operation Handoff/roaming: Move from one cell to another Dynamic configuration: Addition, deletion, and relocation of end systems
without disruption to users
Wireless LAN Requirements
Infrared (IR) LANs: Individual cell of IR LAN limited to single room◦ IR light does not penetrate opaque walls
Spread spectrum LANs: Mostly operate in ISM (industrial, scientific, and medical) bands◦ No Federal Communications Commission (FCC) licensing is
required in USA Narrowband microwave: Microwave frequencies but
not use spread spectrum◦ Some require FCC licensing
Technology
An open, global specification that empowers mobile
users with wireless devices to easily access and interact
with internet information and services instantly.
The wireless industry came up with the idea of WAP.
The point of this standard was to show internet
contents on wireless clients, like mobile phones.
Wireless Application Protocol
WAP is an application communication protocol WAP is used to access services and information WAP is inherited from Internet standards WAP is for handheld devices such as mobile phones WAP is a protocol designed for micro browsers WAP enables the creating of web applications for
mobile devices. WAP uses the mark-up language WML (not HTML)
WML is defined as an XML 1.0 application
Continue…..
To enable easy, fast delivery of relevant information and services to mobile users.
Type of devices that use WAP
Handheld digital wireless devices such as mobile phones, pagers, two-way radios, smart phones and communicators -- from low-end to high-end.
WAP works with most Wireless networks such as: CDPD, CDMA, GSM, PDC, PHS, TDMA, FLEX, ReFLEX, TETRA, DECT, DataTAC, Mobitex.
Purpose of WAP
Leverage existing standards whenever possible
Define a layered, scalable and extensible architecture
Support as many wireless networks as possible
Optimize for narrow-band bearers with high latency
Optimize for efficient use of device resources
Provide support for secure applications and
communication
WAP Architecture Requirements
WWW programming model is optimized and extended to match characteristics of the wireless environment
Utilizes proxy technology to connect between the wireless domain and WWW
Architecture Overview
World-Wide Web Model
WAP Programming Model
WAP Device - Is used to access WAP applications and content. It might be a
PDA, handheld computer.
WAP Client - Entity that receives content from Internet via a WAP Gateway.
This is usually the WAP Browser.
WAP Content/Origin/Application Server - Element in the network where the information or web/WAP
applications resides.
Continue….
WAP Network ExampleWeb Server
WirelessNetwork
WAPProxy
HTMLFilter
WTAServer
WAPClient
WML
WMLHTML
Components of WAP Architecture
Other ServicesAnd Applications
Transport Layer (WDP)
Security Layer (WTLS)
Transaction Layer (WTP)
Session Layer (WSP)
Application Layer (WAE)
GSM CDMA PHS IS-136 CDPD PDC-P FLEX Etc…
General-purpose application environment based on a combination of WWW and mobile telephony technologies.
It defines the user interface on the phone. It contains WML and WTA (Wireless Telephony Application).
Primary objective – interoperable environment. WAE includes a micro-browser (Client software designed to
overcome challenges of mobile handheld devices that enables wireless access to services such as Internet information in combination with a suitable network) server environment which provides◦ WML◦ WML script◦ WTA◦ Content formats
Wireless Application Environment
• WAP provides a markup language and a transport protocol that open the possibilities of the wireless environment and give players from all levels of the industry the opportunity to access an untapped market that is still in its infancy.
• The bearer-independent nature of WAP has proved to be a long-awaited breath of fresh air for an industry riddled with multiple proprietary standards that have suffocated the advent of a new wave of mobile-Internet communications. WAP is an enabling technology that, through gateway infrastructure deployed in mobile operator's network, will bridge the gap between the mobile world and the Internet, bringing sophisticated solutions to mobile users, independent of the bearer and network.
• Backed by 75 percent of the companies behind the world's mobile telephone market and the huge development potential of WAP, the future for WAP looks bright.
Summary
http://en.wikipedia.org/wiki/IEEE_802.11
http://
www.cisco.com/en/US/prod/collateral/wireless/ps5678/
ps6973/ps8382/prod_white_paper0900aecd806b8ce7_
ns767_Networking_Solutions_White_Paper.html
www.palopt.com.au/wap
References
Books◦ Mobile communications: Jochen Schiller, Addison Wesley 2000◦ Understanding WAP:
Official Website (specifications)◦ www.wapforum.org
Technical/Developer Info and tools◦ www.palopt.com.au/wap◦ www.wap.net
Major players◦ www.nokia.com/wap◦ www.ericsson.se/wap◦ phone.com
OpenSource effort◦ www.wapgateway.org (Kannel WAP gateway project)
References
THANK YOU…!!!